His 15-year-old son shot dead four high school friends in 2021. James Crumbley, who gave him his weapon, was found guilty of manslaughter on Thursday, a few weeks after a similar verdict for the teenager's mother.
After a little more than a day of deliberations, the 12 jurors delivered their verdict, according to American media.
James Crumbley, 47, was on trial for his role in his son's killing.
Ethan Crumbley was sentenced to life in 2022 for killing four students at his school in Michigan in the north of the United States.
Found guilty at the beginning of February also of manslaughter, Jennifer Crumbley, the mother of Ethan Crumbley, will see her sentence pronounced on April 9.
The parents were prosecuted for manslaughter resulting from a failure in their legal duty to control the actions of their child, aged 15 at the time of the facts.
They face up to 15 years in prison.
A gun given for Christmas
At her trial, Jennifer Crumbley testified that her husband had brought back a Sig Sauer 9mm caliber pistol as an early Christmas present a few days before the killings.
She said she took her son to a shooting range the next day.
VIDEO.
United States: a mother sentenced after giving a weapon to her son who committed a killing
Despite a summons from parents at the school on the day of the tragedy - the teachers having discovered an "alarming" drawing on Ethan Crumbley's table and advising them to have him psychologically monitored - they left without bringing him home.
Four dead and seven injured
A minor at the time of the facts, Ethan Crumbley was tried as an adult and sentenced in December to life in prison without the possibility of early release.
The teenager pleaded guilty in October 2022 to bringing the gun with 50 bullets in his backpack to his high school and shooting the high school students.
Also readMassacre in Maine in the United States: “We were suspicious of him, he kept practicing shooting”
He killed two girls and two boys aged 14 to 17 and injured six other students and a teacher.
Faced with the number of gun deaths involving minors, pressure is mounting in the United States to punish parents who, often through negligence, allow access to these weapons.